All eucaryotic cells, both plant and animal, have a nucleus surrounded by the cell cytoplasm. The nucleus contains the cellular DNA complexed with protein and termed chromatin. The chromatin, with its associated proteins, constitutes the major portion of the nuclear mass and is organized by the internal protein skeleton of the nucleus, referred to here as the nuclear matrix (NM). The nuclear matrix also is defined as the nuclear structure that remains following removal of the chromatin by digestion with DNase I and extraction with high salt. This skeletal nuclear structure further is characterized by the "interior nuclear matrix" (INM) and the bounding nuclear pore-lamina complex.
Diverse studies have implicated the NM in a wide variety of nuclear functions fundamental to the control of gene expression (For a general review see, for example, Fey et al. (1991) Crit. Rev. Euk. Gene Express 1:127-143). In particular, as described in U.S. Pat. Nos. 4,882,268 and 4,885,236, it is now known that certain nuclear matrix proteins, specifically interior nuclear matrix proteins, are useful as marker proteins for identifying cell types. For example, the presence and abundance of particular INM proteins have been shown to be characteristic of specific cell types and can be used to identify the tissue of origin of a cell or cell fragment present in a sample. One particularly important application of this discovery is the use of marker INM proteins in evaluating metastatic tissue. It is also known that the expression of certain INM proteins is altered in malignant or otherwise dysfunctional cells. The altered expression pattern of these proteins in malignant and/or dysfunctioning cells also makes the proteins and nucleic acids encoding the proteins useful as marker proteins, alone or in combination, for diagnostic purposes and for evaluating tissue viability. U.S. Pat. Nos. 4,882,628 and 4,885,236, issued Nov. 21, 1989 and Dec. 5, 1989, respectively, to Penman and Fey, disclose a method for selectively extracting insoluble INM proteins and their associated nucleic acids from cells or cellular debris and distinguishing the expression pattern of these proteins in a particular cell type by displaying the proteins on a two-dimensional electrophoresis gel. In addition, it recently has been discovered that INM proteins or protein fragments also may be released in soluble form from dying cells. (See PCT Publication WO93/09437, published May 13, 1993).
To date, molecular characterization of the specific proteins of the NM, particularly the INM, remain poorly defined due to the low abundance of these proteins in the cell and their generally insoluble character. The ability to isolate and characterize specific nuclear matrix proteins and the genetic sequences encoding them at the molecular level is anticipated to enhance the use of these proteins and their nucleic acids as marker molecules, and to enhance elucidation of the biological role of these proteins in vivo.
It is an object of this invention to provide genetic sequences encoding INM proteins useful as markers of malignant cell types. Another object is to provide enhanced means for identifying these proteins and their nucleic acids, including RNA transcripts, in samples. Yet another object of this invention is to provide compositions for use in diagnostic and other tissue evaluative procedures. Still another object is to provide genetic and amino acid sequences useful as target molecules in a cancer therapy. These and other objects and features of the invention will be apparent from the description, figures and claims which follow.